This invention relates to a method for manufacturing a power semiconductor device as well as the device thereby manufactured and, more particularly, to a method for manufacturing a power double-diffused metal-oxide semiconductor field effect transistor device and to such semiconductor device.
The semiconductor device, in particular, the double-diffused metal-oxide semiconductor field effect transistor (which shall be hereinafter referred to as "DMOSFET") can be effectively utilized where the transistor is required to be high in the durability, switching speed and noise resisting property.
Further, the DMOSFET is advantageous in that, because of its structure, the current density is high and the ON resistance is low as compared with MOSFET which is not of the double-diffused type. On the other hand, the DMOSFET has been enhancement type, that is, normally-off type, and it has been demanded that, a power MOSFET of depletion type, that is, normally-on type is provided for a use under certain conditions.